This gist contains instructions on setting up FFmpeg and ...
I'm on Ubuntu 16.10, but backported ffmpeg from 17.04 (the one in 16.10 doesn't have VAAPI support). I tried converting a MPEG2-TS file (containing mpeg2 video and ac3 audio) into another MPEG2-TS, but with h264 video instead. The original video is 1080p and has a bitrate of about 15 /s, and I'm trying to decrease it down to around 8 /s.